Device to test synchro circuit and synchro equipment



B. W. RIDLEY 2,434,961

DEVICE TO TEST SYNCHRO CIRCUIT AND SYNCHRO EQUIPMENT Jan. 27, 1948 Filed July 5, 1945 8 Sheets-Sheet l n lll.

INVENTOR. BALDw/N W RJDLEY.

ATTORNEY.

Jan. 27, 1948. I B W, RlDLEY 2,434,961

DEVICE TO TEST SYNCHRQ CIRCUITv AND SYNGHRO EQUIPMENT Filed Jly 3, 1945 8 Sheets-She)et 2 E INVENTOR. Z g. BALDWIN W. R/DLEY.

mi@ LW ATTORNEY` VOLTAGE jan. 2?, 1948 B, W RlDLEY 2,434,961

DEVICE TO TEST SYNCHRO CIRCUIT AND SYNCHRO EQUIPMENT Filed July 5, 1945 8 Sheets-Sheet 3 TRANsM/rrs@ (GENERATon) )NDUCED )N STATDR COILS.

RoToR o/sP/ ACEME/vr (DEGREES) IVENTOR.

B. W. RIDLEY Jan. 27,' 1948.

DEVICE To TEST sYNcHEo CIRCUIT AND sYNcHRo EQUIPMENT 8 Sheets-Skheet 4 IN V EN TOR. BALD w//v W R/DLEX A T TORNE Y.

Filed July 5, 1945 B. w. 'RIDLEY Y 2,434,961

DEVICE TO TEST SYNCHRO CIRCUIT AND SYNCHRO EQUIPMENT Jam.` 27, 1948.

Filed July 3, 1945 8 Sheets-Sheet 5 INVENT AT TORNE Y.

B. W. RIDLEY Jan. 27, 194s.,

DEVICE TO TEST SYNCHRO CIRCUIT AND SYNCHRO EQUIPMENT 8 Sheets-Sheet 6 Filed July 5. 19.45

l/S VOLT SOURCE INVENTOR. BALow/N W RIDLEY.

@Lum

ATTORNE YA Jan. 27, 1948. B, W RIDLEY 2,434,961

DEVICE TO TEST SYNCHRO CIRCUIT AND SYNCHRO EQUIPMENT Filed July 5, 1945 8 Sheets-Sheet '7 S, OPEN CALL LIGHTS ouTAT/zdo/e aoo) "FT-QM@ S3 ETL-J4 S' sz Lvo 53 SHORTED (DIAL Locks 1r/zo yfar! soo) S, M1033 SHORTED I 53 OPEN. (DIAL Lows AroaR len) (ALL L/Gurs our A7 so QR 240) Sfsf s,3 sHoR'rEo S,- 52" 53 OPEN (No ToRUE) (ALL LIGHTS our AT ALL Pos /T/oNs aF Home) INVENTOR. BALDWIN W. R/DLEY.

ATTORNEY.

Jan. 27, 1948. K B. w. RIDLEY 2,434,961

` DEVICE To TEsT SYNCHRC CIRCUIT AND sYNCHRo EQUIPMENT Filed July 3, 1945 8 Sheets-'Sheet 8 s, -52 REVERSE/J.

WRONG RoTATloMANo om.

Loc/rs Ar lzo enano? f jgj 51-53 REVERSED. wRons RoTAT/ou Aun DIAL Locxs AT 60 we 240 5,-53 REVERSED. wko/va RorATlou Aun uw.

Locks AT 0 on /ao 2LT g. E]

5,-52, Sz-Ss, S3-S, REVERSED coRRgcr RoTAT/ou, DIAL LOCKS AT 6o on 24o g. if'

5,-53, 524 53-52 REVERSED. DIA'. Locks A1' 120 on aoo.

' INVENTOR. BALDWIN W. RIDLEY.

TTGRNEY.

Patented Jan. 27, 1948 glnvention relates to an instrument and niethodfor testing .the-:transmitter .and-repeater units and the .circuits :of anelectricalrsynchro type Y of signal transmitting system.

An i obj eet of this-1 invention is vto `providel -a -self contained, portable instrument .by Vmeans of Ysynhlo aunits vra-nd circuits .can vbe 'aceuraigely testediinntheir installed. environment.

ttn otlier object j is :to -vprovide an inexpensive testing devicetliat-will obviate thelneed forusing .a istandard synchroain testingsynchrasystems'.

:A -gfurther olojectis to provide ra testing instrument. withawlnehrrelatively unskilled enerfeief .Gan fiesizferz'an-drectify .defects in a synchro system -zfmerely liyiollowing -Jlisual a indicia]v on the instrument ,inet rautomaticauy indicate 1.the souree Offiheffiefeet and .vtliemeans for thev'eorreeiien ihereei ,A still further-object isfftmprovide an :electrical ireuiimeans .fer contrellablyirotating a :synchro unitzandwhihtlwill transmitffand 'reeiveA synchro signals.-

;Ellllther. objects and advantages L of this :inventiQILas Well alsaitsiconstructionarrangementand operation, will,befanperenifremithefollewing 'desgription ,andclaims .in -k-connectiovn w ithtl1e;ac. emnanyins-drawings, inWhiQh,

Figure ,1 isafrQnt-elevaiien of the'ftesi finstrument showing the instrument :panel land visual indieia .,tirereen,

Figure 2 .is ,a circuit adiaerarn ei :the test Liin.- lsirument,

iisurei .is a. .simplfefireircuit vdiagram nef fthe test cireuitas `4,applied io -a synchro kunit under test,

figure, .5 .is a :eireuit vuwerern of fe, standard Synchro signal .transmitting system,

I'Figure 6 is a diagrammatic illustration ,ofithe voltages induced lin .the stator -windings of a yllenro unitas theo rotor is-vur-nedl FiSilre .'7 :is a diagrammatic view of zthe :in- Sirilmeni Panel vsnor/n in Figure liwith #the pertinent portions of the analyzing chart shown in ,the position --they -would loccupy in analyzing aci-remt `defect,

Figure 8-is :a detailed View -of the chart employed inthey testinstrurnent,

Figuref91is-Aa .phantom view -of a-portion Y,ofgthe test instrument `shown vrin'fFigure 1 showing vthe sligiing mark and its :relation te :the analyzing Qliartand eversng-nswiten, Y

l :Figures Y .01159.13:inclusireillustratefthe ,various analyzing observablefisymptomsain La synchro unitsinewhch .electroalishertsveidst infzthe istatorrwindings offra synchro.. unit 'understestl Figures 114 z to w17 ;:inc,lusive z illustratevthe ,symptoms :apparent :when dan .open circuitrexsts .in the stator-windingslorial synchro i unit underatest,

Figure :18 snows :the :test :circuit zfor the :relectrieal .azern rv-alignment stesi. :and

:EigureSlBito inclusive illustrate athevariqus renditions 0i crossedstator-windings.

f he iermermetilodfitestingsynenrofunits i Y siused. `Bmnoting@the 1er .Qf he rdeyieleibeing tested when Vdriven by iiiissiandardathed erunderztestfmayebe esi-relsedzferiepen hertrcireuitsaandfre versed circuits, etc. The standard ,synchro is @relatively nernensire @and @obtainable and. e skilled, :trained :,onerator, i v Lize he behavior .of @the en @einen ven by eine eine. moreover, is f; A'notdee Sub- K4n f11r1e,asL Qitenieeeurszinfuse aboardship.

Ine testinstrument-reemprisins)this invention isfdesienedtefrepleeeithe standard testsynenro invcendueti .Itieensists-,onlyfof anreleotrieli gnPSFeSAQf g,:;f:ir.euit.eenta1nr ndieeting lights fand switches and fa visual analrzingrorrtrquble sneetinaenart. fzltlisthere 'forelishtran /uegeiiin @Qns -uetorn easiiylnertf able-.a inexpensive.' itis ,sofarransedatha inexnerreneed operate knob 1a. The region of the panel adjacent the slot or opening 6 is suitably inscribed as shown with a number of visual indicia columns or legends. The various legends are in tabulated form with each row related to a cooperating row on the chart' 8 as willbe more fully explained. Each of the rows inscribed on the instrument panel l will he referred to by numerals 11, 12,

13, 14 and 15 respectively. l

The chart as shown in detail in Figure 8 of the drawings consists of 12 vertical columns (labelled A to L) and five horizontal rows (labelled V11 to j 15) corresponding with the visual indicia] rows on the instrumental panel l (Figure 1).- Each of the vertical columns of chart 8 bears two headings reading in degrees between and 360 in steps of 30. The uppermost; headings inbrought to the outside of the instrument box as shown in Figure 1 and suitable extension leads having similar designation are connected thereto for use in testing synchro circuit installations.

In actual service installations all synchro units are connected to terminal blocks such as indicrease in value as read to the right and the lower headings decrease in value. The uppermost heading is used in testing synchro units that have increasing dial scale readings with clockwise rotation, while the lower heading applies to synchro unitsdesigned for counterclockwise rotation, in which the vdial scale readings increase with counter-clockwise rotation of the synchro. Underneath the printed rows (11 to are three colored bands of varying widths separated from each other by colorless margins. These bands are respectively red, ygreen and amber in color as shown Lin Figure 8 and the width of each strip at any point along the chart represents the relative intensity ofthe corresponding indicating light, 3, 4, or 5 with which these color bands are aligned as shown in Figures 1 and 7.

Mounted on the panel of the instrument box l are a reversing switch i6, a zero lock switch I'i and a pair of push-button switches i8 and I9. 'lhese switches as well as the indicating lights are in the test circuit otherwise enclosed within the instrument box and illustrated diagrammatically in Figure 2. The test circuit comprises end terminals Ri-Rz and Si-Sz-Sa. Indicating lamp 5 (amber) is connected across terminals Sz-Ss by leadsY 20 and 2l and green indicating light `l is connected across terminals Si-Sz by leads 2| Vand 22. Red indicating light 3 is connected across terminals Si-Sa by leads 2B, 22 and 23. Terminal R2 is connected by lead 24 to zero lock switch l1 and blue indicating light 2 is connected in series with this lead together with a series resistance 25. The zero lock switch I1 when closed connects terminal R2 to terminal S3 through leads` 26, 23 and 20 and to terminal Si through extension lead 22a oi' lead 22. Switch l1 is a conventional double-pole toggle switch withits common terminal shorted by a jumper lla.

The circuit is provided with means for electrically shorting terminals Si-Sz or terminals Sz-Ss. With switch I6 in fnormal position, Sz is connected through leads 2l and 2l, push-button switch I8, lead 2B, switch I6, and leads 30, 26, 23, and to Sa, or through lead 2l, pushbutton switch i9, lead 29, switch i6, and lead 22 to S1. On the other hand, with switch I6 in reverse position, S2 is connected through leads 2i and 21, push-button switch i8, lead 28, switch I6, and lead 22 to Si, or through lead 2l, pushbutton switch I9, lead 29, switch I6, and leads 3B, 26, 23,-and 20'to Sa The purpose of reversing switch I6 is to permit use of push-buttons i8v and i9 to effectA changes (as indicated on panel i adjacent tosaicl push-buttons) in the cated by numeral V30h in Figure 2 and the connecting leads on the terminal block are labelled with the standard synchro lead designations,

Ynamely Rif-R2 as the rotor leads and Si-Sz-Ss as the three stator leads. A synchro unit comprising the stator winding leads Si-Sz-Sa and rotor leads R1-R2 is' shown in the circuit diagram of Figure 2 connected to the test instrument circuit through terminal block 30h.

A synchro unit is illustrated in Figure 4 and a typical synchro signal transmitting system comprising similar transmitter and receiver units is shown in Figure 5 of the drawings. As shown in Fig. 4, the usual type of synchro unit consists of a housing 3l in which there is rotatably mounted a rotor unit to which the indicating dial 32 is fixed to rotate therewith. The synchro unit shown in Figure 4 is designed for clockwise rotation and is suitably inscribed so that the numerical value in degrees inscribed on the dial 32 will increase with clockwise rotation. External leads Si-Sz-Ss and Ri-Rz are connected to the stator and rotor elements respectively of the synchro unit 3|. Standard terminology is employed to denote the various circuits of all synchro units as shown in Figure 5, to facilitate and standardize wiringr installation. Thus the three stator coils or windings of each synchro unit .are denoted by Si, Sz and S3 respectively as shown in Figure 5 Whether or` not a transmitter or repeater unit is being referred to. Similarly the rotor winding terminals are labelled as R1- R2 as shown. The typical transmitter and receiver unit circuit diagram is shown in Figure 5 to illustrate later discussion. An index 33 (Figure 4) is provided on the mounting panel or case (not shown) in which the synchro is mounted as a reference point of rotation.

The test instrument of this invention employs a series of indicating lights together with a selfexplanatory defect-indicating visual indicia table used in conjunction with a rotatable analyzing chart mounted in alignment therewith so that setting of the analyzing chart in response to an observed abnormal behavior of the instrument under test will automatically indicate in legend form the nature of the defect causing such abnormality.

The test instrument described above is used to locate and rectify the various defects commonly found in an electrical synchro signal transmitting system. These defects include the following:

. Electrical opens in synchro-unit rotor circuit. Electrical shorts in synchro-unit stator circuit, Opens in synchro-unit stator circuit,

. Electrical zero alignment test,

. Stator circuit wiring reversed or mixed,

. Rotor circuit wiring reversed.

In the following disclosure the apparent effects caused by the presence of each ofA the above defects in a synchro system will be describedtogether with .;the manner in whichgtheftestfiinstrnment-gf-t-his inventiam.y `detects and rectiesrsuch defects. l-nconducting ethe test, Jthe iinstrlnnent is connected 5to theterminal iblockf |111v as 'l shown in Figure ;2 with the `test leads :R1-@Ra :and Si-Sa-Ss from theinstrumentbox :connectedaito correspondingly llabelled terminals on the terminal'block at the particularxpoint in the synchro system vat which the. test is A to be conducted. Itewill therefore be seen, fromfaninspectionf'of the circuit. diagram of Figure 22thatfthei-synchro unitunder testis connected inthe=test circuit in accordance with the simpliied testcircuit'ldiagramshown ein Figure '3 of the-drawings.

fRed indicating .light L13 (Figure -3) fis connected across synchro .unit stator terminals`A S1`S3i greengindicating light ."41is connected acrossstator :terminals :Sr-'S2 and; -a-mber Aflight i5 `is-fconnected across stator terminals Sz-#Sa Terminal R1 of lthe synchro .rotor.isfconnectedtogsa and terminal R2 vis connected in series with blueindicating -flight 12 and resistance I2 '5 to Si'and-S: through zero lock switch |11. `Itis `alsofapp'arent from this ligure that byclosing--reyersing switch |6 ineither direction and ractuating -either push button |-8 ycr i9, terminals Si-'Sz and Sz-Sa-respectively can be electrically shorted. The reversing switch |16 is used in y@.Qnnection'with the ,push button switches I8 and I9 selectively to change the'position of 4the-rotor of the synchro undertest,so Vthatgthe legends on-panel'tl adja cent said push-button "switches may be v ccoidinated-with -dial "readings von said synchro thajt increase with Aeither clockwise l(-normal") or counter-clockwise Aifreizerse?) irotation, as :the case may be. The rotoris `*excited from an A. C. power. source connected vt .terminals -Rr-Rz Aas shown. :The construction of a synchrolncludes the threephase Wye-connected statorsfSli, Saand Sa (Figure) and the rotatableA.Qexcitedroter .R1-#Ra Rotation of the rotormemberjRi-Raof either the transmitter or repeater units induces a -sinusoidally Varying current-.inteachmothe stator windings which isgrapicallyfshown by thegcurgvges o fgliignref)` in which eachcurvegshows the mag-- nitride of the voltage in; any one stator winding for aI giyenpositionothe rotor R11-,Ra

.-Inasmuch as lthe'inelicating lights-3.14am 5 are connectedv across terminals S1 S3,,S,1S2and S2-Ss,\1e.spectively, (Fisurep) -themaenitude of the Vvoltages across these terminals as Ythe v:rotor Esi-Rz is rotated,wil1 be indicatedby 4th e.intenf sity qfeach,V of these lights,-,thereby.yisuallynjep; resentingt-he.voltage'curvesof Figure 6. The sequence-in which theseE lights .vary fromdimto brightcan therefore be usedasacheck fcrgthe proper lrotation l of a synchronnit -npa Ilflinllirv subseguently to be described.

.In conducting a test, the analyzing `,c :hart .f8

n (Figure 8) `mounted on the peripherypf-thegrof tatable drum is-used in lconnection withw-.the Visual indicia ori-legends arrangedin column iorm adjacent the sighting slot 6 onthefinstrument panel, and identiedby-gnumerals 11, 12,13, 7.14 and .-15 in Figure 1. The-*analyzing ,chartefis shown in detail in Figure-*8. 'As shown. it consists of :'12 .-vertical columns gidentiied; by letters ALB, C, D; E, F,-G,H,YI, .lL-K, and AL -and a number-of horizontal rows 11,12, 13, 14: 13110115 lwhich Vlcor-- respond respectively to the;1egend-rowsf1l,v1-2, 113,-

14 and 15 inscribed onthe faceqof theinstrument panel Fieure 1).- g'llhe .two topmost hqrizcntal rows :labelled .inFieure ;8 iynchrc dial vreading setherellappear Qpncsite.theiinscrintiQn-fsetf n: dicatlonfhewfattheftoncf-;tnefsiehtinaslet han the ipane'l fCEigure il). 'rEorpurposes-oriilus tration'aportion of ,the instrumentpanelj (Figure l) has been .shewny in-liigiirellY with .thepertinentportions ofthe analyzing chart' 81(1igure'81) namely columns A,"C,"E, G, YIvand'Kshownn as they wouldappearin sighting slot 6 on the in.- strumentboxigFigure 1) when the drumlis rotatedioagiven position in a manner'later tobe described. ltwillbe seen ,from Figureithathy reading across any selected visualindicia row a statement of defect YcanV be read. For example,l if G01-cinefil were tc epnearin the ,Sighting Slot' (Figure ,1-') reading across row"|2 in 'Figurefll there .would vbe `s eenthev statement ",Dial locks atpdsition indicated iSz-'Sa 'in 'stator snorted. This means that'ifg'the test instrument were use'd;'in-,a manner 'later to :be described, the Vabove visual statement -wouldfmake apparent that stator vwijrrdings S2 and Si are-snorted as in`Figure11iandithe operator Awouldimmediatelyv know what` defectin the 'synchro' unitfun'der-test should be corrected. In asimilar mannerthe other 4columns areused to visuallyindicateVarious other defectsas 'Will become apparent in "later portions ,of thefspecication.

The enrst'two horizontal *or* heading rows (Figures and "8) Vofthe analyzing chart 8 appearing opposite (synchro dial Areadings are set here) both-are markedin degrees;the rst commencing With-0 degrees -and increasingin value or correspondingto clockwise Vrotation of the synchro unit dialjzfuigure 4'), the-second decreasingfin value-or `correspondi-ng to counter-clockwisel rotation ofth'esynchro -dial "32. When 'thereVersi-ng switchk |46 4"is in the' fnormal "position, 4a slidable mask 34 connected-tothe Yoperating handle of the reversing switch |6 ris thrown -across the sighting slot '6 (Figure "'1).` 'Suchfaction is illustratedlin Figure .9i-n-which-thefreversing switch |61 isg-shown in^fnormal ,-position. The slidable mask j'34 is slidablymounted on the under face of the -Ltest panelA l. An aperture 35 adjacent oneend of-the maskd'ffits cverftheswitch handle Ia softhat the rnask'willslidebackand forth asthelswitch handle 16a isfthrownfrom normal to reverse positions. linthe-normal position the-offset portionio-the-rnask' 34afwill cover fthe lower -rowo'f figures on A`'the fchart-89s shown in Figure 2 vso thatetfheetop row of-'gureswill bev visible through the sighting slot 6. Similarly when -the handle Ilia oflswitchIB-is 'thrown tothe reverse posi;- tion,"themaskfM-will lbe slid tfo the right so Athat the-toprowonumeralsis masked and the second row visible -t-hrouglhthe sighting-slot' 6. The'purpose pif-this arrangement is vtofadapt the test instrument to test synchros designed for either clockwise `or counter-clockwiserotation. Switch |6 set 1in"-norm al positionfor the former, with the -mask 34i uncoveringA the topmostheading A on chart 8 and is thrown to reverse position in testingthe ,latter vtypes lof .synchros with mask 34 exposing the 4second@oiirtoi gures.

1. ,Tnsfrmc FQROPEN omSHoRT :IN THEfRQ'rpR .CrRcUI'r I [thereis ,an` open in the rotor` coil circuit vnone ofllthe indicating lightsl, ,3. .4 o r v5 will .be.. en`er gized (Eigure 3);.rnoreover there will be no torque in .the roter R14-.Re and the entire .synchro -unit willnot befenergized The-.presenceiofanelectrical shortl in the rotor vcircuit-fwculdbeapnanentas' soon the-.synchro unit were 4 cermectecl .to Athe power source rasta 2. TESTING FOR SHORTS IN rin: S'rA'ron CIRCUIT 1 A short circuit in the stator winding will be indicated by the fact that the dial32 on the indicating unit (Figure 4) under test will lock in any one of 6 positions dependingupon which of the stator windings are snorted, when the synchro is connected to a power source. The reason for this can be seen by referring to Figures 10, 1l, 12 and 13 of the drawings whichshow a typical stator winding with stator coils S1-Sz, Sz--Ss and Si-Sa respectively shorted. With coils S1- Sz shorted as in Figure 10, there will be no voltage across these two terminals and indicating light 4 (Figures 2 and 3), which is connected across these terminals, will be out; the lights 3 and 5 will burn with equal intensity. The rotor will take a position as shown in Figure l aligned with coil Sa such that the dial 32 (Figure 4) will read 240 or 60 degrees. The drum 'l in the instrument box (Figure l) is then rotated by means of the knurled knob 'la until the top row of gures (reading in degrees) on the chart 8 corresponds to the corresponding synchro-unit reading at which the dial stoppedi. e., either 60 or 240 degrees. This has been shown in Figure 7 of the drawings which is a diagrammatic illustration of the instrument box of Figure 1 with the pertinent columns of the analyzing chart 8 shown in their relation to the visual indicia columns on the instrument panel I as they would appear in the sighting slot 6 when the drum 1 is set. Thus, for the condition outlined above, should the dial lock at 60, the drum would be manually rotated until column C (Figure 7 appeared in slot 6 on the instrument panel with numeral 60 opposite Set indication here. Reading across the visual indicia column l2 Diallocks at position indicated S1-S2 in stator shorted would be read. By this means, an operator would immediately ascertain the defect in the synchro unit under test and would know the remedy. Similarly if Sz-Sa were shorted as in Figure 11, light (Figures 2 and 3) would be out and the rotor would assume a position aligned with coil S1 corresponding to 120 or 30() degrees as shown. If it were 120 degrees, then the drum would be turned until column E (Figure 7) were opposite Set indication here and column l2 would read Dial locks at position indicated Sz-Ss in stator shorted. Similarly with the condition illustrated in Figure 12 in which Si-Sa are shorted indicating light 3 would be out, and the dial would lock at either 0 or 180 degrees and columns A or G, Figure 7 would indicate the defect.

With all three windings shorted as in Figure 13 no torque would be evident on the synchro unit and all the indicating lights 3, 4 and 5 (Figures 1, 2 and 3) would be out.

3. TESTING FOR AN OPEN CIRCUIT IN THE STA'roa CIRCUIT Anopen may exist in any one or all of the stator windings S1, S2 or S3 as shown in Figures 14, 15, 16 and 17 of the drawings. The presence of an open circuit in the stator winding would be made apparent upon rotating the synchro unit under test either manually or by the push-button switches I8 and I9, by the fact that indicating lights 3, 4 and 5 (Figures 1 and 7) would not operate in proper alternate sequence as previously described in connection with `Figure 6 of the drawings, but would simultaneously increase and decrease in intensity as the rotor of the synchro unit were turned. By noting the position of the synchro rotor when all three of the indicating lights are out, and making use of the rotating drum 1 and appropriate visual indicia row (11 in Figures 1 and '7) the open circuit can be detected in the following manner:

a. Field winding S1 open as in Figure 14 In this case, all three indicating lights 3, 4, and 5 will be out when the rotor B21- R2 is in a 120 or 300 position as shown in Figure 14 because S1 being open, there is no Voltage across lights 3 and 4, and the voltage across light 5 is almost zero since the flux from rotor Ri-Rz is almost entirely transverse to coils S2 and Ss. Rotating drum l (Figure 1) so that either column E or K. of chart 8 (Figure 7) appears in the sighting slot 6, visual indicia row 11 (Figure 7) will indicate Vthat coil S1 is open.

b. Field winding S2 open as in Figure 15 All three indicating lights 3, d and 5 will be out with rotor Ri-Rz in a 0 or 180 position as in` Figure 15 for reasons similar to those stated in (a) above and columns A or G on chart 8 will indicate that coil S2 is open when Visual indicia row 11 is read (Figure 7).

o. Field winding S3 open as in Figure 16 The three indicating lights 3, d and 5 in this case will be out with rotor Ri-Rz in a 60 or 240 position as shown in Figure 16 and columns 11 and either C or I on chart 8 (Figure 7) will indicate that stator winding S3 is open.

d. Two 'or more yield windings .open as in Figure 17 In this case there will be no voltage across any of the indicating lights 3, 4, or 5 as the rotor Ri-Rz is turned, regardless of the position of the rotor because there is no electrical continuity in the stator circuit.

4. ELECTRICAL ZnRo ALIGNMENT Tss'r In order to have a definite position at which to set the dial 32 of the synchro unit (Figure 4) a deflnite'phase relation between the dial in rela tion to the rotor must be established. That is, a position must be established whereby the dial will indicate zero at a predetermined rotor position so that all synchro units used in a system will eorrespond. This position is known as electrical zero and is dened as Electrical zero is that position of the rotor with respect to the stator in which there is no voltage induced in stator coils S1 and S3 and the Voltage across the rotor terminals Ri-Rz is in phase with the equal voltages across S24-S1 and Sz-Sa respectively." To satisfy this condition the rotor Ri-Rz will occupy a position with respect to stator windings Si, S2 and Sa as shown in Figure 18 and the dial 32 will be positioned on the rotor so that its zero mark will be opposite the reference mark 33 as shown in Figure 4.

The electrical zero test is performed by throwing switchA Il to the zero lock position as indicated in Figure 1 of the drawings. The circuit of Figures 2 or 3 with switch I1 closed may be illustrated in simplified form as in Figure 18. With the synchro unit connected in this manner the rotor R1-R2 will lock electrically in one of two positions, 0 or 180 degrees because there is no voltage across Si-Sa. Should blue indicating light 2 (Figures, 1 and 18), light with the rotorRI- Rz in this position, the rotor ist 180 degrees from electrical zero. By rotating the rotor 9i' Erg-Riz f1801i` degrees :frompthise'position:plight 2 will geput; Thispositioniis electricalazeros` The purpo'setofresistancezSisto preventflampfz from burning-:out in:t the. iuifdegree posi-tion: and insure' fthat,4 the: .1115A :Svolti lampeZ will not` glow at the :lower voltage"whichtexists in'thefzel'ectrcal zero position. When the synchro rotorfR'i-Rz is at thelBOV degree .position therotorand stator voltages are additive. Th ratio' of the stator to tliesrotor windings 'is-1115 to 781f'o'r .astandard Synhro unit rvf1f1--ll1filamp 2 Arwillfheve 2.193 VOUS impressed on it and fwilll light.- At. electrical zero, thek rotor and stator voltages are opposedisathat.

only 37vo1ts isirnpressed on light2 fand :resist-4,. ance-25:soithat theeformerwillfnot light The electrical-zero alignment test is `performed asi-follows;

(a) kISvvitchr I1@ (labeledfiO-jlO. inr.Fig.. 1) e is, thrown to-. zero lock?? position. IfRi y.s tndltz in. the sy-nchrocircuit are, properly Connectedthe dial 32 on the synchro unit under test will locksat either O or 1 80 degrees. `At 0 degreethe blue indieatinglight 2Wil1 b eout'andat 180 degrees it will light as above stated? j Cb) -If,ihcwever,r the:- opposite: shoulduhappen and? blue-indicating lightr4 should light@ whenr-the dial flocks at 'and be 2 outzwhen ,they latterzlocks atl-18,0%- then'; by\rotating drum 'I'until the headfinge180". appears insightingi:slot B; vi'sual indicia row I 5` in the instrument.ipanelA 1I. .wouldreadi-- "Ii indication appears hereRi-TRZ (from column G, Figure?) in' rotor reversed. The defect and remedy-Iis'faccordinglyimade ar'Jparent."

The -st ator Vwi-nding-:circuitlof the synchro unit under test mayrbe m-iXed up` or crossed as fell lows:

ail-S1IVA and S2 may befreversed"asin-Figure19;

bi' S an'dSs-.may loe-reversed as in Figure-'205' lc. Srand S3 may be reversed as in Figure' 2 1 dii SrandlS, S2 andiS'z, andfSa `and"S'r--may be mixed'as :inf Fig'uref 2 2 eslSilandfS; S2 andfSi; andi Si andSi-mayl be Ifif'any two of tlistatr'winding'sfare'reversed in* theV` synchroy unit-urlderjtest,l operation olz sWl'tchesf-I 'I `(labelled f (F180) I 8 (labelled vG0L-240) and |91(iabeiledizosno' consecutively'. womit' cause the rotor Ri-Rz to rotate in a direction opposite tthatfindiatedon' theswitch labels. 'I hatijse instead ofthe rotor rotating clockwisegin G (jlffincreasingfincrements' to correspond witlilthe ewigen layers; itworld; rotate counterclockwise in 60"f decreasing increments exactly oppositeto tlie labelling" on* the j switches IT; I8; and. I9. r.e' spectively. 'Ih'ereason forfthis is' as. follows:

a. If stator windings Si and@Sewarefreversedas shown in Figure 19:

1: Then c1bsing= switch n' actually-'renews Sa to Ss .i (because kof the /crossedfconnection'sl as in Figure. l'Landgthero, tor'willtherefrelck .at a-12O orSOQ degree' positionY insteadof 0'or 1805? in accordance withfthelabelion; the switch.,

2"".- clesinggswitehzletaetuaiiizshortsfsitos;

as in Figure". 10; and nierotreiarwiu lt'icliV at. 60"or 2'40jus`tlasi-tleswtchiis lb'elledl ai `mesme. switch lavmishort sato s1". as in Figure-12,andvr the, rotor dial win lock at 0 or 180 instead of.` 126 orSOIl degreeseas the-.svlritcheislabelled)l Itcan-be seen fromtheabovelthatthedial in. rotatingfrom 12.0 to `60v` to- 0?, etc.,- instead of from 0 -toffil }'.tol20} etc.,y is rotatingin an opposite to normal direction. This will be immediately de l tectedbygclosing switch I'I. which will cause; the

b; If :stator :windingsgSa and Saar-e reversed; (Fig:

ure `x20 1.3.Glosing1switchr :I 1' will; sll'ortfszgtov S1 as in-:Eigure :liandzdialgw-ill lockt-at 60 or 240idegrees(insteadno 0;'or;; 1 80 as labelled in Figure 41),.L 2;*.Switch I8 will'shortf ,Srtof S'a asfinvFigf; urefe12-.anid dialwillglockfat Oior 180 (instead of 6.0-5240asilablledg.-. y 3. Switch.,|9 willeshortsato Sz .as in Figurell .and diaLWiHJockat-IZO or i300, (aslabelledb .1

The .synchroy motor. will? therefore rotate. inv an' opposite direction t-thatf indic'atedfloy fthelabels on switches II, I8. and I9 asftheseswitches are consecutively'actuatedi Therefore-by noting the synchro dial" readingiwhenr switchwII 'is closed'` (60 or v240 degreesin this case) land setting: drum. 6'

with `either* .of vthese: headings (columns aC` or: AI

of fchart- 8, Figure'?) appearing-fin.- tliersighting slot 6," and readingracross indicia' row 13T-it willf be made apparent' that istator winding S2' and Si y are reversedf c. statoriwmdings Si and 's3 .reversed .(Fieure 21)'y 'In this' casaiclosingfswitchi I1 willactually-short Sito S3' andthe synchrofdial' wlllcklat Oor '180 degrees-as in Figure; 12 and` willicorrespond yto-the switch label. Howeverftherotor will'stilrro tate inv a wrongif. direction .asi .will fbev noted byv operatingftheotherzswitches I8`-a'ndI9in line with the' abovetheory; Therefore;v reading indoia rowm13" (Figure y'7 )`V 2in. connection witheith'er columns' A Y or: G" (corresponding: 'to' 0 or 180'Y degreesl' it vfoundthatf coils :Sr and S3:- are' re-V versed.

2; switch la win shares-rte seas inricure-11 I andthe2ciampigeen,alt-1120 or 300 (insteadofi'orZflO/ as lahelled) 3. Switch I9 will 'shor'tSi togSas'in Figure 12 and the dial' will lockjat- Q V'ofrlO (instead of: 12D 0r r 300 as, labelled) 11 when switch i1 is thrown (60 or 240) column 14, Figure 7 Wrong indication, correct rotation" will indicate, in connection with either columns C or I, which are set in the sighting slot 6 that Si-Sz, Sz-Sa and Ss-Si are reversed and should be corrected.

e. Stator windings S1-S3, Sz-Si and Sa-Sz mixed Here again the'synchro rotor would correctly rotate to give increasing dial readings but the rotor dial will not lock at the points corresponding to the switch labels so that:

1. Switch I'I will short S2 to Se as in Figure 11 with the rotor dial locking at 120 or 300 degrecs (instead of or 180 as labelled).

2. Switch I8 will short S3 to Si as in Figure l2 and the dial will lock at 0 or 180 degrees (instead of 60 or 240).

3. Switch I9 will short Si to S2 as in Figure 10 and dial will lock at 60 or 240 degrees (instead of 120 or 300).

Thus when switch I1 is thrown, the dial will lock at 120 or 300 degrees and by setting either column E or K (Figure 7) in the sighting slot 6, indicia column 14 will make apparent that coils S3-Sz, Sz--Si and S143 are reversed and should be corrected.

It will be noted from Figure 8 that the analyzing chart 8 is provided with a band of color strips varying in width. These colors are red, green and amber corresponding to the colors of the indicating lights 3, 4 and 5 (Figures 1 and 7) on the instrument panel I. The color strips are separated by black bands (to indicate no light) and the width of each color strip at any given point along the chart is proportional to the intensity of the corresponding indicating light.

In a preceding-portion of the specification it was mentioned that the voltages existing in each winding S1, S2. and S3 respectively of the synchro stator vary in accordance with the curves shown in Figure 6 and that the indicating lights 3, 4 and 5 respectively, being connected across each of these stator windings gave a visual representatiori of these voltages by their respective intensities as' the synchro rotor was rotated. In other words, if the synchro unit under test were correctly connected and in proper condition, as the rotor Ri-Rz (Figure 3) was turned clockwise,

a. The test instrument is connected to the synchro unit asl before and the synchro rotor is then rotated in 30 or 68 degrees increments manually. l

b. The drum 1 is rotated so that the headings on the analyzing chart 8 (Figure 7) appearing in the sighting slot 6 correspond with the synchro dial readings.

c. The intensity of the indicating lights 3, 4 an 5 is compared with the widths of the Ycorresponding color bands on the analyzing chart 8 appearing in the 'sighting slot 8. Theyshould correspond and follow in sequence with the lights. If the color bands do not correspond with the lights an existing defect in the synchro circuit is made apparent and the visual indicia on the instrument panel I are referred to, for analyzing the defect as before.

n 6. SUMMARY or I'rzsrmc PROCEDURE Testing for opens in synchro stator circuit Testing for electrical short in synchro stator circuit Synchro dial will lock at a position depending on which stator coils are shorted, and indicating light across the shorted coils will be out, the other two burning with equal intensity. Set drum and analyzing chart to correspond with synchro dial reading and refer to visual indicia row 12.

Testing for reversed stator windings a. If any two stator windings are crossed, operation of switches I1, I8 and I9 in sequence will cause opposite rotation of synchro dial and the dial readings at which the rotor stops will not correspond to the labels on these switches. Set analyzing chart in sighting slot to correspond with synchro dial reading and refer to visual indicia column 13 on test instrument panel I (Figures 1 or 7).

b. If all three stator windings are mixed, the synchro dial will rotate correctly, upon actuation of switches I1, I8 and I9 in succession, but the dial readings at which the dial stops will not correspond to the labels adjacent these switches (Figure 1). Set analyzing chart in sighting slot 6 to correspond with synchro dial reading and refer to visual indicia column 14 on the test panel i. Y

Electrical zero alignment test If, on actuating switch I'I (Figure 1) the dial on the synchro reads 0 degrees and blue indicating light 2 is on, and light 2 is out upon rotation of the synchro dial to degrees, then set analyzing chart so that 180 degree heading ap pears in sighting slot 6 and refer to visual indicia row 15 on test panel I.

General check of synchro transmitter operation Rotate synchro unit and drum, comparing the sequence and intensity of indicating lights 3, 4 and 5 with the color scheme on the analyzing chart 8.

The test instrument comprising this invention has been shown and described in connection with a simple synchro circuit. It is obvious that it also can be used'in testing the more complex synchro circuits employed such as a differentialsynchro or control-transformer-synchro circuit since the theory of synchros applies equally well to the latter types of circuits. The color scheme employed on the chart 8 and indicating lights 3, i and 5 are by way of illus- 13 tration only, since it isobyious that `any convenlenty color scheme, or other indicating System similar tothat described could be substituted.`

Itisto be understood that various modiiications and changesmay be made inthis invention without departing from the spirit ,and scope thereoiasset forth inthe appended claims.

The inventiondescribed herein may be manuactured and used by or for the Government of the; UnitedStates of America for governmental purposes without the payment ofany royalties thereon or. therefor.

What is claimed is:

l. An instrument for testing synchro circuits employing synchro units having a stator winding .and a rotatable single-phase eld winding comprising, in combination, an electrical-test circuit including voltage-indicating means adapted to be connected across the stator windings ofthe synchro unit under test, and a circuit-defect analyzing device comprising a Visual indiciascale having legends correlated with said voltage-indicating means andthe movement ofA said synchro-unit rotor, and an adjustable chart having symbols pertaining to said synchro circuit and being ad- ,instableV to correspond with the various positions assumed by the synchro eld windingwhereby defects made apparent by the voltage-indicating means and the behavior of the rotatable eld of such-synchro as the latter is rotated are visually analyzed and defined by the combined readings of said visual indicia legends andsaid symbols on said analyzing chart.

2; An instrument for testing synchrocircuits comprising, an instrument panel having a plurality of defect-indicating visual indicia columns, an analyzing chart movably mounted on saidtest paneladjacent said visual indicia columns and in cooperative relation therewith, visual symbols on said analyzing chart aligned with said visual indicia columns, an electrical test circuit mounted on said test panel, for connection to the synchro under test, electrical indicating means in said test circuit and visible on said test panel, portions of said visual indicia columns having legends related to said electrical indicating means and the behavior of the synchro unit under test,

, which when read in connection with corresponding visual symbols on said analyzing chart define the nature of the defect in said synchro circuit indicated by said electrical indicating means.

3. An instrument for testing electrical circuits comprising an instrument panel, an electrical test circuit mounted on said instrument panel, electrically actuated indicating means in said test circuit, said indicating means being mounted on said panel for visual observance thereof, a sighting slot in said panel, a series of defect indicating visual indicia legends adjacent said sighting slot arranged in tabular form, an analyzing chart movably mounted underneath said panel and visible in part through said sighting slot, and a series of symbols tabularly arranged on said analyzing chart, said symbols denoting various components of the circuit under test, the portions of said symbols Visible through sai-d sighting slot being aligned with correlated portions of said visual indicia legends on said panel adjacent said sighting slot, whereby defects in the circuit under test made apparent by visual observance of said electrical indicating means may be defined and analyzed by visual reference to said legends on' said test panel together with said symbols on said analyzing chart visible through said sighting slot.

' tricalswtch means` for connecting the synchro eldin parallel with. said synchro stator wind.- ing switch means for selectively electrically shortingadjacentphases ofstator windingselectricallyv actuatedl visible indicating; means con-f nected across Aadjacent phasesoi said stator Winding; and in. series with said rotatable eld, and reversing switch meansfor reversing the relation betweenphases .of the stator, winding.

5. In. an instrument for testing synchro units of the typef having apolyphase. Wye-connected stator windingv and a single-phase rotatable-field windingtowhich a` dial havingvgraduations is secured, thecombination of. an electricalY test circuit. having leads for connection to 4the windings of the synchro unit .under test, voltage-indicating means and electrical switch means inrsaidtest circuitzand a circuit-defect analyzingv chart comprising columnarly arranged visual indiciaA representing Avarious conditions` of said voltage-indicating means andthe rotatableeldof said. synchro unit under test', and anadjustable'analyzing chart consisting of a number of columns of sym.- i

bolseach of saidcolumns having as aheading one ofsaidgraduations and the symbols of which denote the-elementsofthe synchro windings under test, saidanalyzing chart being adjustable relative -tofsaid.visualindicia so that each of said columns of symbols can be selectively aligned with said visual indicia' corresponding to a given position ci"V said synchro rotor, whereby defects madeapparent by said voltage indicating means and thel behavior of saidrotatable ield winding are-analyzedand defined by thecombinedreadings of anK appropriate column .of said `Visualrindicia and the portion` of said symbols on said analyzing chart aligned therewith.

6. An instrument for testing synchro circuits Iof the type employing synchro units having calibrated dials, said instrument comprising a test panel having a plurality of defect-indicating visual indicia columns, an analyzing chart movably mounted on said test panel adjacent said visual indicia columns, said analyzing chart being provided with a plurality of columns of visual symbols each of which has as a\heading one of the calibrations of a dial of a unit of a circuit to be tested, an electrical test circuit mounted on said test panel for connection to said synchro circuit under test, and electrical indicating means in said test circuit and visible on said test panel, actuation of said test circuit operating said synchro units in the synchro circuit under test and simultaneously energizing said electrical indicating means, said indicating means in said test circuit visually making apparent defects in said synchro circuit, whereby when said analyzing chart is moved to a position corresponding to the dial position of the synchro under test at which the defect is made apparent, portions of said visual indicia columns having indicia related to said electrical indicating means, will dene together with a corresponding portion of said analyzing chart adjacent said legend, the nature electrically connecting said test circuit to the lleads of said synchro unit under test, said test circuit including electrically actuated visual indieating means and Switch means mounted on said instrument panel, said indicating means and said switch means being connected across adjacent phases of said polyphase stator winding in the synchro unit under test by said test circuit and one of said indicating means being connected in series with said synchro unit rotor, each of said switch means when closed, selectively electrically shorting the corresponding adjacent phases of said stator to which connected thereby to produce rotation of said synchro rotor in 60 degree increments, said indicating means at all times indicat- -ing the magnitude of the voltages across the corresponding phases of said stator to which connected, and defect analyzing means on said instrument panel in the form of visual indicia whereby defects made apparent by the operator of said switch and said electrical indicating means are visually analyzed and defined by said visual indicia.

8. A circuit tester comprising a, plurality of visible indicia indicating a plurality of defects possible in a circuit to be tested, an analyzingr chart movably mounted with respect to and adjacent said indicia and in cooperative relation therewith, various visible symbols on said chart having at various positions of said chart obvious relationship with said indicia, an electrical test circuit for connection with the circuit to be tested, electrical indicating means in said test circuit and simultaneously visible with said indicia and chart,'portions of said indicia comprising legends related to said indicating means and the behavior of the circuit under test, which when read in connection with the corresponding chart symbols dene the nature of a defect in said circuit indicated by said indicating means.

9. For use witha synchro unit having relatively rotatable single-winding and plural-winding members, apparatus for testing said unit for circuit continuity comprising a circuit including a source of energy and rst switch means for connecting the single-winding member in parallel with the plural-winding member, second switch means for normally selectively eiecting shortcircuiting connections between predetermined windings of the plural-winding member, indicating means connected to each of the windings of the synchro unit, and reversing switch means for altering said normal short-circuiting connections between said predetermined windings.

' 10. Apparatus for testing a synchro unit for circuit continuity, said unit having relatively rotatable parts, one of said parts being of the plural-winding type, said apparatus comprising first switch means for effecting short-circuiting connections across adjacent windings of said one part, second switch means for connecting the other part in parallel with said plural-winding part, and individual indicating means connected across said adjacent windings and in series With the other part of said unit.

' l1. The apparatus defined in claim 10 further characterized by means for altering the shortcircuitlng connections across said adjacent windings.

BALDWIN W. RIDLEY.

REFERENCES I'rED The following references are of record in the i'lle of this patent:

UNITED STATES PATENTS Number Name Date 1,648,410 Lawton Nov. 8, 1927 2,352,499 Sears June 27, 1944 

